This invention relates to sequential flotation of sulfide ores and, more particularly, to the sequential and selective initial flotation of the copper component directly from ores containing copper sulfide and the sulfides of other metals such as molybdenum.
Western United States porphyry ores contain copper sulfide and molybdenite or molybdenum sulfide as well as the sulfides of other metals. Many operations have been developed for recovering the molybdenite from the copper concentrate by a number of different separation processes. Typically, the majority of existing copper-molybdenum processes first float a combined copper-molybdenum bulk concentrate using a lime circuit and then employ one or more processes to separate the copper and molybdenum. These various processes may include steam or roasting heat treatment, the use of reagents such as sodium ferro and/or ferricyanide, sulfide reagents and arsenic or phosphorous Nokes' reagent, hypochlorite or hydrogen peroxide oxidation, long conditioning periods or bulk concentrate aging, and other methods coupled with many stages of cleaning.
Thus, sodium hydrosulfide, sodium sulfide or ammonium sulfide are used to depress the copper sulfides while floating molybdenite with a hydrocarbon oil. Nokes' reagents, which are thiophosphorous or thioarsenic compounds, have been widely used in the separation of molybdenite from copper, causing depression of copper minerals. In this process, the bulk copper-molybdenum concentrate is treated with the depressant to inhibit flotation of the copper and iron sulfides, while the molybdenite is floated with a hydrocarbon oil and a frother. Oxidizing agents such as hypochlorite or permanganate have been used with the final stages of upgrading of the molybdenite concentrate requiring the additional use of ferrocyanide, sodium cyanide, or a zinc-cyanide complex. The combination of hypochlorite and sodium ferrocyanide has been used as has hydrogen peroxide in conjunction with sodium ferrocyanide. A steaming process has been used whereby the copper-molybdenum bulk concentrate after thickening is steamed at atmospheric or higher pressures to strip the collector coatings from the mineral particles. This is followed by flotation using ferrocyanide for additional depression of the copper sulfides, with a light hydrocarbon oil and an alcohol frother used to recover the molybdenite. Roasting has been used for removal of collector coating and superficial oxidation of the copper sulfide surfaces. Dextrin and starch have been used to depress the molybdenite while floating the copper sulfides.
U.S. patents concerned with the recovery of molybdenite from copper sulfide-molybdenite concentrates include U.S. Pat. Nos. 2,664,199 and 2,811,255.
There remains a need for improved methods for the direct flotation of copper from ores containing the sulfides of copper, molybdenum and other minerals and, in particular, for effecting a primary selective flotation of copper by direct treatment of such ores rather than by the initial formation of a bulk copper-molybdenum concentrate.